The present disclosure relates generally to warning light devices, and more particularly to optical configurations for producing integrated directional light from a LED light sources.
While not limited thereto in its utility, the novel technology to be described below is particularly well suited for use in combination with light emitting diodes (LED's) and, especially, for use in warning and signaling lights.
Commercially available LED's have characteristic spatial radiation patterns with respect to an optical axis which passes through the light emitting die. A common characteristic of LED radiation patterns is that light is emitted in a pattern surrounding the optical axis from one side of an imaginary plane containing the light emitting die, the optical axis being oriented perpendicular to this plane and emanating from a center of the die. Typically, the light generated by an LED is radiated within a hemisphere centered on the optical axis, with a majority of the light emitted at angles close to the optical axis of the LED. Although the quantity of light emitted typically declines as the angle relative to the optical axis of the LED increases, light emitted at angles greater than approximately 45° represents a significant portion of the overall light output of the LED. The distribution of light radiation within this hemisphere is determined by the shape and optical properties of the lens (if any) covering the light emitting die of the LED. Thus, LED's can be described as “directional” light sources, since all of the light they generate is emitted from one side of the device, with the other side dedicated to a support that provides electrical power to the LED and conducts heat away from the die.
When designing light sources for a particular purpose, it is important to maximize efficiency by ensuring that substantially all of the generated light is arranged in a pattern or field of illumination dictated by the end use of the device into which the light source is incorporated. The somewhat limited overall light output of individual LEDs frequently necessitates that several discrete LED components be cooperatively employed to meet a particular photometric requirement. Use of arrays of LEDs and their directional emission pattern present particular challenges to the designer of warning and signaling lights. Employing LEDs in compact arrays additionally imposes cooling, i.e., “heat sinking”, requirements which may not be present in the case of prior art warning and signal light design.